On March 28, the water used to cool a “containment vessel” in the atomic plant at Three Mile Island, in Middletown, Pennsylvania, grew dangerously hot and gave every sign of growing hotter. The consequences were as follows. The company that owned the plant, Metropolitan Edison, did everything it could to solve the problem quietly, and in the process released large quantities of radioactive material into the air and water surrounding the plant. Their efforts having proved an utter failure, they reported the accident several hours late to the Nuclear Regulatory Commission, which in turn allowed two days to pass before dispatching a team of experts to the site. In adding a delay of its own to that of Metropolitan Edison, the NRC appears to have been actuated by the same motive: the smaller the fuss over the accident, the less considerable the danger would seem in retrospect. The NRC team on arriving at the site found something approaching total chaos. From the mass of contradictory reports, however, it finally emerged that the worst imaginable calamity for a nuclear plant—a “core meltdown,” which would release into the air a radioactive cloud, killing tens of thousands and injuring hundreds of thousands more, within a radius of at least 50 miles—had become a not entirely remote possibility. Governor Thornburgh ordered the evacuation of children and pregnant mothers wi...